Room: Davidson Ballroom B
Purpose: To develop and validate a methodology for pharmacokinetic modeling of hyperpolarized [1-13C]-pyruvate to probe tumor metabolism in vitro. This method is meant to serve as a foundation for translation and validation of in vivo pharmacokinetic modeling strategies of [1-13C]-pyruvate imaging.
Methods: We developed a closed-system pharmacokinetic model for the conversion of hyperpolarized pyruvate-to-lactate to characterize aerobic glycolysis in vitro. The model was applied to an anaplastic thyroid carcinoma cell-line (Hth83, ~30 million cells/experiment), by quantifying the dynamic conversion of hyperpolarized [1-13C]-pyruvate-to-lactate, using a 300-MHz nuclear magnetic resonance (NMR) spectrometer (Spectrospin 300; Bruker Biospin) and doxycycline to reduce lactate dehydrogenase (LDH). A dynamic nuclear polarizer (HyperSense; Oxford Instruments) was used to produce hyperpolarized pyruvate. A hyperpolarized pyruvate dissolution (125ÂµL, 1-mM pyruvate conc.) was added to Hth83 cells in a 10-mm NMR sample tube. Dynamic 13C spectra were acquired (TR=2s & FA=15Â°) and exported to Matlab for pharmacokinetic modeling. Additional Hth83 cells were treated with doxycycline (0.1â€“1.0Âµg/mL) for 48 hours to knock-down LDH activity and lactate production. Normalized lactate (nLac, normalized by pyruvate) was quantified using the lactate and pyruvate spectra, and the apparent hyperpolarized pyruvate-to-lactate rate constant, Æ˜PL, was determined by pharmacokinetic analysis of the signal evolution.
Results: Control cell experiments (untreated, n=9) showed highest nLac, followed by 0.1 Âµg/mL (n=7) and 1.0 Âµg/mL (n=6) of doxycycline-treated cells (meanÂ±SD=0.153Â±0.05, 0.106Â±0.049, 0.087Â±0.050, respectively) (P=0.012, 0.049, & 0.025, respectively). Æ˜PL was highest for control cells, followed by 0.1 Âµg/mL and 1.0 Âµg/mL of doxycycline-treated cells, (0.805Â±0.571, 0.451Â±0.375, 0.224Â±0.139, respectively) (P=0.018, 0.150, & 0.010, respectively). Normalizing each nLac by total cell count per experiment yielded a linear trend with Æ˜PL (R=0.80).
Conclusion: Our methodology can serve as a fundamental approach to robustly probe tumor metabolism using hyperpolarized [1-13C]-pyruvate imaging and doxycycline in vitro.
Not Applicable / None Entered.